The objectives of this study are: 1) to observe whether the natural history of chronic obstructive respiratory disease and functional respiratory impairment correlates with long-term exposure to photochemical oxidants, 2) to measure the sensitivity and specificity of selected tests of lung function, and 3) to determine if specific tests of lung function are particularly sensitive to changes resulting from chronic exposure to photochemical oxidants. These objectives will be met by observing changes in lung functions over five years in residents of four areas exposed to different levels and types of air pollutants. Comparison of test results at baseline examination suggest that residents exposed to high levels of photochemical oxidants and residents exposed to high levels of primary pollutants have poorer lung function than residents exposed to low levels of air pollutants. We are now measuring changes which have occurred in the two cohorts exposed to the lowest levels of air pollutants including specific subgroups of these populations, e.g., children, smokers, non-smokers, individuals with pre-existing disease, etc. It is our intention to also reexamine the two cohorts exposed to the highest levels of air pollutants in order to determine if a relationship exists between progressive respiratory impairment and long-term exposure to photochemical oxidants.